Though John Cleese had nothing to do with it :), this movie is different from any other feature film I've yet seen on IA, and different from most other films I've seen.
For one thing, there is no real structured plot to tie the story together. Instead, episodic vignettes are presented in a "days in the life of..." fashion, the life being that of Zoe Jensen, played by Michael Learned (best known for playing mama Walton, as already mentioned). What gives these events continuity and ties them together is the timeline of her involvement in a church choir that is practicing for a special Christmas performance of Handel's Messiah.
Interestingly enough, she plays no role of extra significance in the choir (she doesn't even try out as a soloist) and, despite the uploader's/IMDb description, she is never shown to interact with the choirmaster (played by John Houseman). Her only real significance in the movie is that she is more or less the anchor character: the people whose lives we are shown are the people who have entered her world in various ways (mainly through the choir).
It's not even possible to say that her people are shown "through here eyes" (that is, from her point of view). If this were a novel instead of a movie, it would be described as written almost entirely in the third person (the "omniscient narrator"). There are some scenes where Zoe doesn't even appear. In that sense, it is not even possible to say that it is entirely her story.
An approach like this might look like an aimless screenplay where the author(s) couldn't decide on just what the movie was about. My take is that it is about the ordinary lives of ordinary people who embark on an extraordinary venture: training under the discipline and guidance of an experienced and competent choirmaster with the aim of performing classical music to a symphonic orchestral standard.
There are more than three story threads here, just as there are many story threads in the lives of most people. They make friends, have disagreements, show quirks (even to kleptomania) and egos, occasionally deliver remarkable homespun wisdom, and sometimes get in sufficient trouble to blow themselves out of the story. Most of the cast are character actors who give the appearance, at least, of needing to do little more in the way of acting than just to be themselves. At least in my case, it works because there is absolutely no suspension of disbelief required whatsoever.
John Houseman plays the choirmaster in this film similarly to how he played a law professor in The Paper Chase
(I suspect that's why they cast him in this), but also differently. He does play the same strict disciplinarian, but doesn't terrorize his choir members the way he did his law students (no funeral shroud ceremony :D ). The screenwriters clearly understood music production (and art production in general), and wrote both his character and the choir scenes accordingly. I have not seen another film where the craft[wo]manship aspect was clearly identified as such, even in films that portray the production of music, art, and motion pictures. Everything else he had to say about music (including its intensely mathematical nature) was spot on. All of this added even more reality to an already realistic film. (And by the way, if he looks like a curmudgeon and perfectionist, try reading up on some of the stories about Arturo Toscanini!)
Saving the best for last, there is the music itself. Classical music is not all that common a topic for mass-market motion pictures. For anyone who has some background in this music, even as a listener, the film becomes twice as rich. There really is drama in hearing a collection of moans, wails, and quavering voices (sorry, couldn't resist) become a tight and sharp complex harmony. Drama, too, in saving a vandalized junior relative to the mighty thundering pipe organ (if you've ever heard the recordings of E. Power Biggs playing Bach Fugues and Toccatas, you'll know what I mean), so as not to have to use a poor electronic imitation. (Can you hear the difference? I sure can!) There are even two operatic voices—one strong and dramatic, one lyrical and perhaps even coloratura—who audition for the spot of soprano soloist. At the end, the lyrical soprano who is chosen does sing the birds right out of the trees.
If you're still with me by now, you might get the idea that I liked this film from my not being able to say enough good things about it. Seeing people being people is good for the soul; hearing the music that comes into being against all the odds is a treat both for the soul and the ears.